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+--- Thread: Test of the Olympus M.Zuiko Digital 24 mm f/4 ED Fisheye ;) (/showthread.php?tid=3044)
Test of the Olympus M.Zuiko Digital 24 mm f/4 ED Fisheye ;) - Tiz - 08-06-2011
Canon does the same with the SX220/230. In fact, the lens is wider than 28mm.
I also believe that the Panasonic 14mm is actually wider.
Irrespective of the focal length there is still the disadvantage that you have less resolution after distortion correction. For example, the Canon SX220 has only about 10-11 MP (instead of 12 MP) after distortion correction. The image is then "bloated back" to 12 MP by way of extrapolation. Probably, the loss in resolution is slightly less in the case of mFT.
Test of the Olympus M.Zuiko Digital 24 mm f/4 ED Fisheye ;) - Klaus - 08-06-2011
[quote name='dave9t5' timestamp='1312658742' post='10435']
The article claims that they checked the field of view:
"It’s also worth mentioning here the field of view issue. We measured it for JPEG files using the method of panoramic sequence and the sky photo method - taking angular distance measurements between stars of the celestial sphere. Both methods produced the same result of 73.7 degrees on the longer side (with the margin of error not exceeding 0.2 of a degree) so exactly as much as we expect from a 12 mm lens on a 4/3 sensor. You should remember that the field of view in RAW files will be by several degrees wider. "
So seems the true focal length is "several" degrees wider. I don't know if it's always the case for m4/3 manufacturers to accurately label their lenses' corrected focal lengths or the true focal length. It must be tempting to label the true focal length (which cheats the user), so kudos to Olympus for being a bit more truthful about the effective focal length. Or is there a standard for m4/3 focal length labeling?
[/quote]
Well, the focal length is the focal length is the focal length. This is a physical spec. I agree that this is meaningless from a user perspective though.
I still keep on wondering why they did it. Olympus manufactured some of the finest lenses around in the FT scope and now they are free floating some abberations which they should be able to master based on their design capabilities. We are not talking about a budget lens here.
Test of the Olympus M.Zuiko Digital 24 mm f/4 ED Fisheye ;) - Tiz - 08-06-2011
[quote name='Klaus' timestamp='1312662890' post='10437']
Well, the focal length is the focal length is the focal length. This is a physical spec. I agree that this is meaningless from a user perspective though.
I still keep on wondering why they did it. Olympus manufactured some of the finest lenses around in the FT scope and now they are free floating some abberations which they should be able to master based on their design capabilities. We are not talking about a budget lens here.
[/quote]
In my opinion, it's because of size. A lens with less distortion would be significantly larger and heavier. It would make no sense to use it on a small mFT body. If you are prepared to use large and heavy lenses, you can also go APS-C or even fullframe.
The Sony NEX is affected even more by this problem. Therefore, I am curious to know whether the NEX 7's sensor will use the rumored micro lenses to overcome the problem and, if yes, whether this will work. I believe the sensor of the Leica M9 also uses microlenses for distortion correction?
Test of the Olympus M.Zuiko Digital 24 mm f/4 ED Fisheye ;) - popo - 08-06-2011
[quote name='Tiz' timestamp='1312663200' post='10438']
I believe the sensor of the Leica M9 also uses microlenses for distortion correction?
[/quote]
That corrects for negative effects from shallow angle of light hitting the sensor. Distortion isn't one of them though.
Test of the Olympus M.Zuiko Digital 24 mm f/4 ED Fisheye ;) - popo - 08-06-2011
[quote name='Brightcolours' timestamp='1312627852' post='10425']
http://www.lenstip.com/310.6-Lens_review-Olympus_M.Zuiko_Digital_12_mm_f_2.0_ED_Distortion.html
Nice little lens.. but my goodness, it is basically totally uncorrected. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/ohmy.gif' class='bbc_emoticon' alt=':o' />
[/quote]
I see what you did with the title! <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/tongue.gif' class='bbc_emoticon' alt='
' />[quote name='Klaus' timestamp='1312629270' post='10427']
This is quite a letdown for such a pricey non-pancake lens.
[/quote]
I'm in two minds about this... how much can we sacrifice for other benefits? If we allow lenses to have some easily post correctable flaws, can we get them smaller/cheaper or even perhaps more easily optimised for faster focus by less moving elements. But the price is certainly putting it in a premium position, so perhaps we would wish for more there.
As a side note, while I like the AF/MF design on this lens, and would love to see it on more, I fear they'll only do it on premium lenses.
Test of the Olympus M.Zuiko Digital 24 mm f/4 ED Fisheye ;) - Brightcolours - 08-07-2011
[quote name='Tiz' timestamp='1312649666' post='10434']
I agree. Not twice. I just wanted to emphasize that also the center is affected. If you just cut the corners, the image size will be reduced from 4000*3000 to maybe 3850*2900 (4:3 12MP example). If you now save the image, you will not have a 12 MP image. But the cameras and also Adobe Lightroom do not do that. They save a full 12 MP (4000*3000) image. Therefore, it is necessary to extrapolate the entire, cropped image. I am wondering about the impact on IQ (depending on the extrapolation algorithm). In any case, I do not like the idea.
[/quote]
No, you do not really have to affect the center.
The edges are what needs "correcting" by stretching them, basically. This leaves the center more or less unaffected. You end up with a larger image, pixel resolution wise. Then you crop this to original pixel resolution.
You can (some software applications do that, and I think PS does that too in its lens correction module)) also shrink the center. and leave the edges relatively resolution unaffected, and end up with a smaller image... but that is not what is the smart thing to do usually.
Test of the Olympus M.Zuiko Digital 24 mm f/4 ED Fisheye ;) - Brightcolours - 08-07-2011
[quote name='popo' timestamp='1312664153' post='10440']
I see what you did with the title! <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/tongue.gif' class='bbc_emoticon' alt='
' />I'm in two minds about this... how much can we sacrifice for other benefits? If we allow lenses to have some easily post correctable flaws, can we get them smaller/cheaper or even perhaps more easily optimised for faster focus by less moving elements. But the price is certainly putting it in a premium position, so perhaps we would wish for more there.
As a side note, while I like the AF/MF design on this lens, and would love to see it on more, I fear they'll only do it on premium lenses.
[/quote]
The lens is not so small though, and not so cheap either...
Comparing it to the "ancient" Canon Ef 24mm f2.8 on 135 format ("full frame") this Canon is 1 stop faster (the Oly being 24mm f4 equivalent), the Oly is 43 x 56mm, the Canon 48 x 67mm. So basically a difference you would expect for a lens that is a stop slower.
But the Canon is much better corrected.
So I am not so sure here the "uncorrected" design has much to do with benefits in other areas... just a philosophy that they correct in software rather than in lens design.
Test of the Olympus M.Zuiko Digital 24 mm f/4 ED Fisheye ;) - Tiz - 08-07-2011
"The edges are what needs "correcting" by stretching them, basically. This leaves the center more or less unaffected. You end up with a larger image, pixel resolution wise. Then you crop this to original pixel resolution."
It seems to me (but I am not sure) that this is not what's happening with the Canon SX220. I have not tried any other cameras. The maximum resolution of the sensor is 12 MP (4000*3000). This is the distorted image. If you now start to correct the distortion, you will have to crop a certain amount of the edges (?) and, consequently, the cropped image will have less than 4000*3000 pixel (can be easily tested if you work with RAW files). If you shoot .jpg the camera nevertheless saves a corrected 4000*3000 pixel image. But this can only be because the image was extrapolated (aka bloated back to the orginal size)? It might be a bit different with a 12MP sensor that can actually record more than 4000*3000 pixel.
Test of the Olympus M.Zuiko Digital 24 mm f/4 ED Fisheye ;) - Brightcolours - 08-07-2011
[quote name='Tiz' timestamp='1312713184' post='10446']
"The edges are what needs "correcting" by stretching them, basically. This leaves the center more or less unaffected. You end up with a larger image, pixel resolution wise. Then you crop this to original pixel resolution."
This is not what's happening with the Canon SX220. I have not tried any other cameras. The maximum resolution of the sensor is 12 MP (4000*3000). This is the distorted image. If you now start to correct the distortion, you will have to crop a certain amount of the edges and, consequently, the cropped image has less than 4000*3000 pixel (can be easily tested if you work with RAW files). If you shoot .jpg the camera nevertheless saves a corrected 4000*3000 pixel image. But this can only be because the image was extrapolated (aka bloated back to the orginal size). It might be a bit different with a 12MP sensor that can actually record more than 4000*3000 pixel.
[/quote]
You do not get the principle yet.
With the distortion, the corners/edges are "squashed". Not the center.
So... if you stretch the edges, to correct the distortion, you end up with a BIGGER image, pixel resolution wise. Which you then can crop to original pixel resolution. The center "optical" resolution remains mostly untouched.
You can NOT test that easily with RAW files, if you only have software that corrects if by shrinking the center of the image, instead of expanding the edges. So, not sure why you think you know what your SX220 does internally. All you know is what the RAW converter does that you are using.
With expanding the edges, you lose sharpness on the edges. With shrinking the center you lose sharpness in the center due to the shrinking, and then later too if you expand the resulting image to the original pixel resolution. Expanding the edges/corners is the smartest thing to do, and that is most probably what Olympus and Panasonic are doing.
The MTF measurements to suggest that too, with the edges trailing the center resolution with a considerable and quite uniform over the aperture range difference.
Test of the Olympus M.Zuiko Digital 24 mm f/4 ED Fisheye ;) - Tiz - 08-07-2011
Thanks. Got it and I agree.
(Unfortunately, you quoted the first version of my post which was edited about 5 secs later ; )